That script is essentially stuck in the olden days of the Kobo OG and/or Kobo Touch. Don't use it.
TL;DR:
* If you actually intend to work with the *stock* Qt & QPA, use NickelTC (or build a Dockerless version of it from my scripts, c.f.,
https://github.com/pgaskin/NickelTC/issues/2 where we just discussed something like that). I'd link to my binaries for this, but, IIRC, the final one is the *sole* file that got eaten by the dreaded OVH fire

.
* If you don't, use koxtoolchain & the kobo target. Possibly with a custom Qt5 build & QPA (c.f., UMR & InkBox) if you *really* want new Qt.
So, a good start would be asking *what*, exactly, you're intending to do?